HTTPS for sender domains

This week we're installing HTTPS certificates for the tracking domains of
all our customers. We use the Let's Encrypt API
to get a certificate for every registered sender domain. This allows us to
secure all hyperlinks from all the mailings that are sent from our servers.

This means that you no longer have to register certificates yourself, and that
you no longer have to get in contact with our support team to ask us to install
or renew a certificate. This all now happens automatically. And because
Let's Encrypt's service is free, we also offer this service free of charge.